The Upshot of the Fourth Way

The heart of the Fourth Way, as I interpret it, is a simple argument:

1. In every possible world, God is the cause of the actual existence of all other actually existent things. (From the Second and Third Ways).
2. The cause of something's existence must be at least as noble, true, and good as the thing itself. (Aristotle's principle from Metaphysics 2)
3. Therefore, God is a noble, true, and good as anything could possibly be.

 
Why think that the Aristotelian principle is true? And what does it mean for something to be truer, nobler, better, or “more existent” than another? We have already seen an appeal to the proportionality of causes in the First and Second Ways. A cause must “have” what it “gives” in some way, either “formally” (by literally have the same characteristic) or “eminently”. Applying this to existence, we could say that the cause of the existence of x must exist either in the same way as x or in a “higher” way.
 
What do “higher”, “nobler” or “better” mean in this context? They must refer to a real, objective hierarchy, not just to our subjective preferences or interest. They must mean something like: having a wider array of powers and capabilities. As Kenny suggests, this corresponds to something like having a more powerful set of cognitive capacities. Despite what Kenny says, St. Thomas’s argument does not depend on everything’s lying on a strictly linear order. It’s okay if some pairs of things are not comparable in their degree of being, so long as there are some things that are strictly nobler than everything else (a common peak in the “Mountain of Being”).
 
I should say something briefly about Aristotle and Aquinas’s notion that some beings are “truer” than others. As Aquinas explains, “true” can be used in two ways: to refer to a cognition that corresponds to some reality, and to a reality that corresponds to some cognition. My idea of a triangle is true if it accurately represents triangles. A triangle is “true” (as a triangle) if it accurately corresponds to the definition of triangle. What would it be for a thing to be “truer” than another thing (as an existing thing)? It might be that it corresponds more accurately to the full, unqualified concept of Being as such. If so, the more nearly perfect or the nobler a thing is, the truer it is.